The Weekly Volcanic Activity Report: November 11 - 17, 2020

The Weekly Volcanic Activity Report: November 11 - 17, 2020

New activity was reported for 4 volcanoes from November 11 to 17, 2020. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Merapi, Central Java (Indonesia) | Whakaari/White, Island North Island (New Zealand).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Helgrindur, Iceland | Ibu, Halmahera (Indonesia) | Pacaya, Guatemala | Sabancaya, Peru | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Snaefellsjokull, Iceland | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan).

New activity/unrest

Karymsky, Eastern Kamchatka (Russia)

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images during 7-9 and 12 November. An explosion on 8 November produced an ash plume that rose to 8 km (26,200 ft) a.s.l. and drifted 230 km NE. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Klyuchevskoy, Central Kamchatka (Russia)

KVERT reported that Strombolian activity at Klyuchevskoy continued during 6-13 November and lava advanced down the Apakhonchich drainage on the SE flank. Gas-and-steam emissions contained some ash and during 7-9 November drifted 85 km E. A large bright thermal anomaly was identified daily in satellite images. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale) on 8 October.

Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters. This volcano is located within the Volcanoes of Kamchatka, a UNESCO World Heritage property.

Merapi, Central Java (Indonesia)

BPPTKG reported that during 6-12 November sometimes dense white emissions from Merapi rose as high as 250 m above the summit. The report noted that the lava-dome volume was an estimated 200,000 cubic meters based on analyses of drone images captured on 3 November. Avalanches of material traveled 3 km down the WSW flank in the Putih/Sat drainage at 1450 on 8 November. Photos from 11 November showed no changed to the morphology of the lava dome in the summit crater. Electronic Distance Measurement (EDM) data continued to detect shortening between points in the NW at a deformation rate of 10 cm per day. Seismicity was higher than the previous week.

On 13 November BPPTKG noted that avalanches had been traveling 1-3 km down the N and NW flanks, indicating summit instability. Authorities recommended no activities within 5 km of the summit. BNPB reported that as of 15 November more than 1,800 residents from the surrounding districts of Boyolali, Magelang, Klaten, and Sleman had been relocated to shelters. Livestock was also being relocated, particularly from three villages within 7 km of the summit. PVMBG noted that less than a dozen rock avalanches were heard at observations posts during 15-17 November. The Alert Level remained at 3 (on a scale of 1-4).

Geological summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Whakaari/White, Island North Island (New Zealand)

Following a period of severe weather, on 11 November GeoNet reported some mainland observations of darker plumes and deposits on webcams; scientists conducted an overflight of Whakaari/White Island on 12 November to investigate. Aerial observations confirmed the presence of ash in the emissions, originating from the main steam vent at the back of the crater lake. An initial analysis indicated that the ash was from loose material around the vent being entrained into the gas-and-steam plumes. The Volcanic Alert Level was raised to 2 and the Aviation Color Code remained at Yellow reflecting greater unrest at the surface.

There was no notable change in the location and size of active vents, though rainwater had created a small shallow lake on the floor of the 1978/90 Crater. A small earthquake sequence and several episodes of slightly increased volcanic tremor were recorded the previous week; the seismic data and observations were unusual for the volcano and may be coincident with the ash in the plume. Gas output was higher than previous recent observations; carbon dioxide flux was 2,390 tonnes/day and sulfur dioxide flux was 618 tonnes/day. The Wellington VAAC noted that the gas, steam, and ash plumes rose to1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted E and SE during 12-14 November, based on satellite data, reports from pilots, and GeoNet.

Small amounts of ash continued to be present in emissions seen during an overflight on 16 November. Laboratory data showed that the particulates were hydrothermal minerals and old volcanic material, with no fresh magmatic ash signatures. Carbon dioxide flux was 1,937 tonnes/day and sulfur dioxide flux was 710 tonnes/day, overall slightly lower than the previous measurement but still above background levels. Seismicity remained similar to the previous week, characterized by a sequence of small earthquakes, a larger than normal volcanic earthquake located close to the volcano, and ongoing low-level volcanic tremor. Re-suspended ash to 460 m (1,500 ft) a.s.l. that drifted E and NE was reported by the VAAC during 16-17 November.

Geological summary: ​The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Ongoing activity

Aira, Kyushu (Japan)

JMA reported that during 9-16 November incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. Two explosions on 10 November produced ash plumes that rose as high as 1.6 km above the crater rim and ejected bombs 600-900 m away from the crater. An eruptive event at 0708 on 16 November generated a plume that rose 1.3 km. The Alert Level remained at 3 (on a 5-level scale).

Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Dukono, Halmahera (Indonesia)

Based on satellite and wind model data, the Darwin VAAC reported that during 11-17 November ash plumes from Dukono rose to 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted NW, SW, and S. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.​

Ebeko, Paramushir Island (Russia)

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 6-13 November that sent ash plumes up to 3 km (10,000 ft) a.s.l. and drifted NE and SE. A thermal anomaly was identified in satellite images during 7-8 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Helgrindur, Iceland

IMO reported that the Alert Level for Helgrindur was raised from Gray (insufficient monitoring) to Green (normal, non-eruptive) on 12 November, reflecting the recent installation of three seismic stations along the peninsula. The new instruments will allow for better coverage and sensitivity for the detection of seismic unrest. The Alert Level scale consists of five colors.

Geological summary: Helgrindur (also known as Lysuhóll or Lysukard) is one of Iceland's smallest volcanic systems. It consists of a chain of small alkali olivine basaltic cinder cones and vents along a WNW-ESE line cutting across the central Snaefellsnes Peninsula in western Iceland. The slightly arcuate line of Quaternary vents extends to the northern coast of the peninsula. Helgrindur is the central of three volcanic systems occupying the peninsula. The latest eruption is undated, but the volcanic field has been active during the Holocene.

Ibu, Halmahera (Indonesia)

PVMBG reported that on most days during 10-16 November ash plumes were visible rising 200-800 m above Ibu’s summit and drifting in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.​

Pacaya, Guatemala

INSIVUMEH reported that Strombolian activity and lava effusion continued at Pacaya during 10-17 November. Explosions from the cone in Mackenney Crater ejected material as high as 300 m above the vent. Lava flows on the SW flank varied in length between 800 and 1,200 m during 11-13 November. Visual observations overnight during 13-14 November revealed a new lava flow from a vent higher up on the SW flank. In a special report issued on 15 November CONRED and INSIVUMEH stated that lava effusion had increased on the SW flank. Avalanches of material traveled as far as 500 m and generated plumes of ash; a white-and-blue gas plume rose 450 m above the summit. Strong explosions at the summit crater ejected material 300 m high. The two parallel flows, 300-1,000 m long, were active through 17 November.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Sabancaya, Peru

Instituto Geofísico del Perú (IGP) reported a daily average of 54 explosions at Sabancaya during 9-15 November. Gas-and-ash plumes rose as high as 3.3 km above the summit and drifted NE, N, and NW. Eleven thermal anomalies over the crater were identified in satellite data. Minor inflation continued to be detected in areas N of Hualca Hualca (4 km N) and on the SE flank. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Santa Maria, Guatemala

INSIVUMEH reported that a moderate explosion at Santa María's Santiaguito lava-dome complex was recorded at 0715 on 16 November and produced an ash plume that rose 1.1 km above the complex. Pyroclastic flows descended multiple directions; the longest one reached the upper part of the San Isidro drainage. Ash plumes drifted SW.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semeru, Eastern Java (Indonesia)

PVMBG that at 0921 on 11 November an ash plume from Semeru rose 300 m above the summit and drifted S. Weather conditions prevented views of the volcano during most of 10-17 November. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.

Sheveluch, Central Kamchatka (Russia)

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 6-13 November. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Sinabung, Indonesia

PVMBG reported that during 10-12 November activity at Sinabung was characterized by ash plumes that rose as high as 2 km above the summit, pyroclastic flows that traveled 1.5-2.5 km E and SE, and block avalanches that traveled 200-1,000 m E and SE. Sometimes dense white plumes rose 200-500 m above the summit during 14-16 November. Block avalanches descended the E and SE flanks as far as 1 km during 14-15 November. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Snaefellsjokull, Iceland

IMO reported that the Alert Level for Snaefellsjokull was raised from Gray (insufficient monitoring) to Green (normal, non-eruptive) on 12 November, reflecting the recent installation of three seismic stations along the peninsula. The new instruments will allow for better coverage and sensitivity for the detection of seismic unrest. The Alert Level scale consists of five colors.

Geological summary: Ice-clad Snaefellsjökull volcano anchors the western tip of the isolated Snaefellsnes Peninsula in western Iceland. Numerous pyroclastic cones dot the flanks of this stratovolcano, the only large central volcano in this part of Iceland. Lower-flank craters produced basaltic lava flows and upper-flank craters intermediate-to-silicic material. Holocene lava flows extend to the sea over the entire western half of the volcano. Several Holocene silicic eruptions have originated from the summit crater. The latest dated eruption took place about 1750 years ago; several lava flows may be even younger.

Stromboli, Aeolian Islands (Italy)

INGV reported that during 9-15 November activity at Stromboli was characterized by ongoing explosive activity from Area N (North Crater area) and in Area C-S (South-Central Crater area). Explosions from the N1 vent (Area N) ejected lapilli and bombs 80-250 m high, and produced ash emissions. Explosions at three N2 vents (Area N) ejected a mix of coarse and fine material at a rate of 6-10 events per hour. Explosions from vents in Area C-S also ejected fine material 150 m high at a rate of 1-2 events per hour.

A series of at least four explosions began at 2104 on 10 November with a major, six-minute-long explosion in the southern part of Area C-S. The event ejected pyroclastic material which fell radially and along the Sciara del Fuoco, and produced a vertical ash plume. Within 30 seconds a second pulse of activity from the central crater area ejected coarse material 300 m above the vent and then produced in tense lava fountaining. A small explosion from vent N2 concluded the series. During an overflight the next day, scientists identified thermal anomalies from lava at the bottom of the S1 and C craters (central part of crater terrace) and craters N1 and N2. A small lava flow from S1 was also visible, and a small hornito (h1) had formed just outside the crater. A second hornito (h2) had formed on the south flank of N2.

A series of major explosive and landslide events began at 1017 on 16 November and lasted for four minutes (based on the seismic signals). Explosions produced a dense ash cloud that rose 1 km, and within minutes caused ash and lapilli to fall in the town of Stromboli, about 2 km away on the NE coast of the island. A pyroclastic flow rapidly descended the Sciara del Fuoco to the NW coastline and expanded 200 m over the sea surface.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium. This volcano is located within the Isole Eolie (Aeolian Islands), a UNESCO World Heritage property.

Suwanosejima, Ryukyu Islands (Japan)

JMA reported nighttime incandescence and intermittent eruptive activity at Suwanosejima’s Ontake Crater during 6-13 November. A total of 35 explosions were recorded, ejecting bombs up to 700 m from the crater and producing gray-and-white plumes that rose 1.8 km above the crater rim. Ashfall was periodically reported in Toshima village (4 km SSW). The Alert Level remained at 2 (on a 5-level scale).

Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Source: GVP


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